A cover member for push-button switches with multiple keys (push buttons) for manipulation of switches is used in the portable terminal equipment such as cell phones and personal digital assistants (PDAs). The multiple push buttons forming the cover member for push-button switches are arranged in a keypad made of an elastomer member such as silicone rubber.
Incidentally, there are strong desires for downsizing of the portable terminal equipment and strong desires, particularly, for reduction of thickness of the key unit. For meeting such desires, the thickness of the keypad made of the elastomer member is recently reduced to the extreme.
The portable terminal equipment adopts a back-lighting function using a light source such as LED, in order to enhance visibility in dark places. In such portable terminal equipment, in order to enhance uniformity of light emitted from the light source, an optically transparent elastomer member is used as the keypad. However, reduction in the thickness of the optically transparent elastomer member leads to failure in exhibiting satisfactory lightguide performance.
Consequently, a lightguide member made of a highly transparent hard resin with high lightguide performance was separately formed and this lightguide member was incorporated between the keypad and the key tops. This achieved an improvement in the lightguide performance. However, it resulted in deteriorating working efficiency of assembly with increase in the number of parts. Furthermore, it is difficult to secure a space for the lightguide member in the recent downsized low-profile portable terminal equipment.
There is thus a proposal, for example, on a luminescent cover as shown in FIG. 7, as a hard base-key unit (cf. FIG. 1 in Japanese Patent Application Laid-Open No. 2003-178639).
The luminescent cover 10 shown in FIG. 7 is used in combination with a circuit board 20. This luminescent cover 10 is provided with a hard base 12, a keypad 15, and a key top 17. The hard base 12 is made as a hard resin plate having a through hole 11. This hard base 12 is provided with an insert port for insertion of a light emitting device 13 at any desired position.
The keypad 15 is made of a rubberlike elastomer film and has a press projection 16. The keypad 15 is integrated with the hard base 12 through an adhesive. A portion of the keypad 15 closes the through hole 11 of the hard base 12. The press projection 16 formed on the keypad 15 is provided for turning on and off a metal dome switch 21 on the circuit board 20. The key top 17 is disposed on the top surface of the keypad 15.